Preparation of cobalt molybdate nanoparticles; Taguchi optimization and photocatalytic oxidation of Reactive Black 8 dye

Theoretical and Experimental Study of Structural Phases in CoMoO4†

“…The unit cell parameters for these CoMoO 4 phases are shown in Table 1. Two different phases have been observed: CoMoO 4 (I) (space group C2/m, No.12), which corresponds to the first modification observed in the literature (ICSD #23808) [8] -sometimes called α-CoMoO 4 -, and CoMoO 4 (II) (space group C2/m, No.12), which is the second phase found in the literature at standard pressure (ICSD #78328) [9] -sometimes called β-CoMoO 4 . The observed diffraction peaks are in good agreement with the values given in the ICSD (Table 1).…”

“…But this structure candidate might also be connected to the orthorhombic Co 2 Mo 3 O 11 [36] structure, which is a compound often observed in the synthesis of CoMoO 4 . (Note that in the original publication, [36] it was also suggested that the composition might be Co 2 Mo 3 O 12 .)…”

“…CoMoO 4 -PRD8 exhibits facemonocapped octahedra with seven-fold coordination of oxygen atoms around Co 2+ , while Mo 6+ cations are four-fold coordinated by oxygen atoms in a tetrahedral arrangement. However, CoMoO 4 -PRD8 has been found in less than 1% of the minimizations during the global optimization. Nevertheless, there might be some structural relationship to the experimentally observed hydrated CoMoO 4 x H 2 O structure.…”

“…This reaction belongs to a group of double-exchange reactions, which proceed at room temperature after the mixture of reactants has been mechanically activated via mixing by hand in a mortar, for a very short time. During this reaction, on the one hand the nitrate and ammonium groups react with the Na from the NaOH, and on the other hand, www.advancedsciencenews.com www.crt-journal.org the free Mo and Co react with oxygen taken from the ambient atmosphere, producing CoMoO 4 .…”

“…Although there exist a large number of high-quality experimental studies on CoMoO 4 compounds, [1][2][3][4][5][6] there are many open questions regarding individual experimentally observed phases, the α → β phase transition, which phase should be properly denoted α or β, respectively, and the temperature conditions at which they are obtained. [7][8][9][10][11][12][13][14][15] A very important issue is the development of a cost-and-time effective method for the preparation of nanostructured cobalt molybdenum oxide with precise control of particle size.…”